E3000 ~ spontaneous port forwarding IP changes

Question

I have an E3000 with firnware 1.0.04. 
A forwarded port is spontaneously changing the IP address assigned to it, but with no change indicated in the singel port forwarding configuration.
I have a web server on IP=XXX.XXX.XXX.7, and another device on my LAN with an internal web server at IP= XXX.XXX.XXX.8.  The single port forwarding configuration is:
        HTTP, external port 80, internal port 80, protocol=TCP, to internal IP address xxx.xxx.xxx.7, enable checked
The configuration is saved, and all works well for for hours and/or days and I can use the web host from the intenet as expected.  However, after a few days or hours the E3000 suddenly starts sending the http traffic to IP=xxx.xxx.xxx.8 instead of xxx.xxx.xxx.7.  When I log in to the router and look at the port forwarding page, it still says it's forwarding the http traffic to xxx.xxx.xx.7 ~ even though all http traffic is being sent to xxx.xxx.xxx.8!  I have to reboot the router to get the port forwarding to work properly.  If I leave the device at xxx.xxx.xxx.8 powered off, the router seems to work fine for extended periods.
There are no port forwarding services in the router that reference IP=xxx.xxx.xxx.8 , and it does not appear that the port forwarding problem is related to DHCP.  All devices on my network have a reserved DHCP address based on their MAC.  It does not appear that the spontaneous port forwarding change occurs when when the xxx.xxx.xxx.8 device powers up and gets it's address via DHCP.  I have also deleted the xxx.xxx.xxx.8 device from the DHCP reservation table and simply access the device as needed by referencing it's IP, and xxx.xxx.xxx.8 is outside the range of DHCP assigned addresses, and the spontaneous port redirection still occurs once in a while.
Is there a known bug where forwarded ports are sent to the wrong IP address?  Is there a fix in the works?  Is there other data I can gather that might help?

Answer 1

Thanks for the reply.  I have a bunch of services running on several hosts, so configuring each port to forward to the proper host using the E3000 single port forwarding page is the only way to go.  It has been 4 days with uPNP turned off on the host (uPNP is still active in the router), and the problem has not occurred as yet.  However, sometimes it has taken over a week for the problem to occur.  So far things are looking good, and I am starting to believe that this host has been "stealing" port 80 by remapping it in the router via uPNP, albeit for reasons I do not understand.
Because a uPNP device can change the port-to-DestinationIPAddress map in the router, the router really should be able to display the actual port map rather than just displaying the desired configuration.  Not being able to see the actual mapping make as much sense as not being able to not see actual DHCP assignments and only being able to see the desired DHCP configuration.  With the widespread deployment of uPNP, and considering the programming simplicty needed to display some table entries from the router's memory, this would seem an obvious and easy feature to add to the next firmware release.  A log of runtime configuration changes would be appreciated too, so that people can ascertain what device on the LAN caused a router configuration change and record what the changes were.  This sure would make troubleshooting a lot easier...